Variable are in scope if they are defined on the page in question or in somewhere in the parent hierarchy of the page in question.

For example, lets say the variable we are interested in is X.
 * If X is defined on this page then it is definately in scope.
 * If X is not defined on this page but is defined in the page .FitNesse (this page's parent), then X is still in scope.  
 * If X is defined on .FitNesse.UserGuide then X is not in scope because .FitNesse.UserGuide is not a parent of this page.

